JP7198041B2 - battery - Google Patents

Description

The present invention relates to batteries.

As one type of battery, a secondary battery, particularly a non-aqueous electrolyte secondary battery, has been developed. A nonaqueous electrolyte secondary battery includes a positive electrode, a negative electrode, and a separator. A separator is positioned between the positive and negative electrodes.

Patent Literature 1 describes an example of a separator. The separator comprises a polyethylene microporous membrane and heat resistant porous layers on both sides of the polyethylene microporous membrane. The heat-resistant porous layer contains an inorganic filler consisting of polymetaphenylene isophthalamide and aluminum hydroxide.

Patent Literature 2 describes an example of a separator. The separator includes a polyethylene microporous membrane and porous layers on both sides of the polyethylene microporous membrane. The porous layer contains an inorganic filler composed of meta-type wholly aromatic polyamide and α-alumina.

Patent Documents 3 and 4 describe examples of separators. The separator includes a polyethylene porous film and a heat resistant porous layer on the polyethylene porous film. The heat resistant porous layer contains liquid crystalline polyester and alumina particles.

Patent Document 5 describes improving the resistance of a battery to a crushing test. Patent Document 5 specifies the tensile elongation of the positive electrode, the negative electrode, and the separator in order to improve the resistance to the crushing test.

JP 2009-231281 A JP 2010-160939 A Japanese Patent Application Laid-Open No. 2008-311221 JP 2008-307893 A JP 2010-165664 A

The inventors have found that it is sometimes difficult to achieve both high rate and high safety in batteries. Specifically, the inventors have found that reducing the thickness of the active material layer of the electrode (e.g., positive electrode or negative electrode) for high rates can reduce the nail penetration test resistance (i.e., safety) of the battery. I found out.

One example of the object of the present invention is to achieve both high rate and high safety. Other objects of the present invention will become apparent from the disclosure herein.

According to one aspect of the invention,
an electrode capable of functioning as a positive electrode or a negative electrode;
a separator including a base material and an insulating layer;
including
The electrode comprises a current collector having a first surface and a second surface opposite to the first surface, and an active material layer positioned on the first surface of the current collector and having a thickness of 60 μm or less. and including
A battery is provided in which the ratio of the thickness of the insulating layer to the thickness of the base is 1.50 or more and 3.00 or less.

According to the above aspect of the present invention, both high rate and high safety can be achieved.

1 is a top view of a battery according to an embodiment; FIG. FIG. 2 is a cross-sectional view taken along the line AA′ of FIG. 1; 3 is an enlarged view of a portion of FIG. 2; FIG.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, in all the drawings, the same constituent elements are denoted by the same reference numerals, and the description thereof will be omitted as appropriate.

FIG. 1 is a top view of a battery 10 according to an embodiment. FIG. 2 is a cross-sectional view taken along the line AA' of FIG. FIG. 3 is an enlarged view of a portion of FIG. 2 does not show the exterior material 400 shown in FIG. 1 for the sake of explanation.

An outline of the battery 10 will be described with reference to FIG. Battery 10 includes positive electrode 100 , negative electrode 200 and separator 300 . Separator 300 includes substrate 310 and insulating layer 320 . In the example shown in FIG. 3 , insulating layer 320 is on both sides (first side 312 and second side 314 ) of substrate 310 . Positive electrode 100 includes current collector 110 , active material layer 122 and active material layer 124 . Current collector 110 has a first surface 112 and a second surface 114 . The second side 114 is opposite the first side 112 . Active material layer 122 and active material layer 124 are located on first surface 112 and second surface 114 of current collector 110, respectively. Negative electrode 200 includes current collector 210 , active material layer 222 and active material layer 224 . Current collector 210 has a first surface 212 and a second surface 214 . The second side 214 is opposite the first side 212 . Active material layer 222 and active material layer 224 are located on first surface 212 and second surface 214 of current collector 210, respectively. Each of active material layer 122, active material layer 124, active material layer 222, and active material layer 224 has a thickness of 60 μm or less. The thickness of the insulating layer 320 with respect to the thickness of the base material 310 (in the example shown in FIG. 3, the thickness of the insulating layer 320 (insulating layer 322) on the first surface 312 of the base material 310 and the thickness of the second surface The ratio of the insulating layer 320 (total thickness of the insulating layer 324) on 314 is 1.50 or more and 3.00 or less.

According to the configuration described above, it is possible to achieve both a high rate and high safety. Specifically, in the configuration described above, each active material layer (active material layer 122, active material layer 124, active material layer 222, or active material layer 224) of each electrode (positive electrode 100 or negative electrode 200) has a high rate of Therefore, it is thin as described above. Specifically, the shorter the distance between the two surfaces of the active material layer (the surface on the side of the current collector and the surface on the opposite side), the smaller the electrical resistance between the two surfaces of the active material layer. A large current can flow between both sides of the The inventors have found that when the thickness of the active material layer is thin, the resistance to the nail penetration test (that is, safety) may decrease due to the low resistance between the two surfaces of the active material layer. The present inventors studied a structure for improving the nail penetration test resistance, and as a result, focused on the ratio of the thickness of the insulating layer 320 to the thickness of the base material 310, and when this ratio is within the range described above, It was found that the nail penetration test resistance was improved.

In the example shown in FIG. 3 , insulating layer 320 is on both sides (first side 312 and second side 314 ) of substrate 310 . In other examples, insulating layer 320 may be on only one of the two sides (first side 312 and second side 314 ) of substrate 310 . Also in this example, the ratio of the thickness of the insulating layer 320 to the thickness of the base material 310 can be 1.50 or more and 3.00 or less.

Details of the battery 10 will be described with reference to FIG.

Battery 10 includes a first lead 130 , a second lead 230 and a sheath 400 .

The first lead 130 is electrically connected to the positive electrode 100 shown in FIG. The first lead 130 may be made of aluminum or an aluminum alloy, for example.

The second lead 230 is electrically connected to the negative electrode 200 shown in FIG. The second lead 230 may be made of, for example, copper, a copper alloy, or nickel-plated material.

In the example shown in FIG. 1, the exterior material 400 has a rectangular shape with four sides. In the example shown in FIG. 1 , the first lead 130 and the second lead 230 protrude from one common side of the four sides of the exterior material 400 . In another example, the first lead 130 and the second lead 230 may protrude from different sides (for example, sides opposite to each other) among the four sides of the exterior material 400 .

The exterior material 400 accommodates the laminate 12 shown in FIG. 2 together with an electrolytic solution (not shown).

The exterior material 400 includes, for example, a heat-fusible resin layer and a barrier layer, and may be a laminated film including, for example, a heat-fusible resin layer and a barrier layer.

The resin material forming the heat-fusible resin layer may be, for example, polyethylene (PE), polypropylene, nylon, polyethylene terephthalate (PET), or the like. The thickness of the heat-fusible resin layer is, for example, 20 μm or more and 200 μm or less, preferably 30 μm or more and 150 μm or less, more preferably 50 μm or more and 100 μm or less.

The barrier layer has, for example, a barrier property such as prevention of leakage of an electrolytic solution or entry of moisture from the outside. It may be a barrier layer formed by The thickness of the barrier layer is, for example, 10 μm or more and 100 μm or less, preferably 20 μm or more and 80 μm or less, more preferably 30 μm or more and 50 μm or less.

The heat-fusible resin layer of the laminated film may be one layer, or two or more layers. Similarly, the barrier layer of the laminated film may be one layer, or two or more layers.

The electrolytic solution is, for example, a non-aqueous electrolytic solution. This non-aqueous electrolyte may contain a lithium salt and a solvent that dissolves the lithium salt.

Lithium salts are, for example, LiClO4, _LiBF4 , _LiPF6 , _{LiCF3SO3 , LiCF3CO2 , LiAsF6} , _LiSbF6 , _LiB10Cl10 , _LiAlCl4 , LiCl, _LiBr , _{LiB ( C2H5} ) ₄ , CF ₃ SO ₃ Li, CH ₃ SO ₃ Li, LiC ₄ F ₉ SO ₃ , Li(CF ₃ SO ₂ ) ₂ N, lithium lower fatty acid carboxylate, and the like.

Solvents that dissolve lithium salts include, for example, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and methyl ethyl carbonate. carbonates such as (MEC) and vinylene carbonate (VC); lactones such as γ-butyrolactone and γ-valerolactone; ethers such as trimethoxymethane, 1,2-dimethoxyethane, diethyl ether, tetrahydrofuran, and 2-methyltetrahydrofuran sulfoxides such as dimethylsulfoxide; oxolanes such as 1,3-dioxolane and 4-methyl-1,3-dioxolane; nitrogen-containing solvents such as acetonitrile, nitromethane, formamide, dimethylformamide; methyl formate, methyl acetate, acetic acid Organic acid esters such as ethyl, butyl acetate, methyl propionate, and ethyl propionate; phosphate triesters and diglymes; triglymes; sulfolane such as sulfolane and methylsulfolane; sultones such as 1,3-propanesultone, 1,4-butanesultone and naphthsultone may be used. These substances may be used alone or in combination.

Details of the laminate 12 will be described with reference to FIG.

The laminate 12 includes multiple positive electrodes 100 , multiple negative electrodes 200 and separators 300 . The plurality of positive electrodes 100 and the plurality of negative electrodes 200 are alternately stacked. In the example shown in FIG. 2, the separator 300 is folded back in a zigzag manner so that a portion of the separator 300 is positioned between the adjacent positive electrode 100 and negative electrode 200 . In another example, a plurality of separators 300 spaced apart from each other may be positioned between adjacent positive electrodes 100 and negative electrodes 200 .

Details of each of the positive electrode 100, the negative electrode 200, and the separator 300 will be described with reference to FIG.

The positive electrode 100 includes a current collector 110 and an active material layer 120 (an active material layer 122 and an active material layer 124). Current collector 110 has a first surface 112 and a second surface 114 . The second side 114 is opposite the first side 112 . The active material layer 122 is on the first surface 112 of the current collector 110 . The active material layer 124 is on the second surface 114 of the current collector 110 .

Current collector 110 may be formed of, for example, aluminum, stainless steel, nickel, titanium, or alloys thereof. The shape of the current collector 110 may be, for example, foil, flat plate, or mesh.

Active material layer 120 (active material layer 122 and active material layer 124) contains an active material, a binder resin, and a conductive aid.

The active material contained in the active material layer 120 (the active material layer 122 and the active material layer 124) is, for example, LiNi _a M _1-a O ₂ (M is selected from Co, Mn, Al, Na, Ba and Mg). At least one element selected.) (For example, lithium-nickel composite oxide, lithium-nickel-cobalt composite oxide, lithium-nickel-manganese composite oxide, lithium-nickel-aluminum composite oxide, lithium- nickel-sodium composite oxide, lithium-nickel-barium-composite oxide, lithium-nickel-magnesium composite oxide, lithium-nickel-cobalt-manganese composite oxide, lithium-nickel-cobalt-aluminum composite oxide, lithium- Nickel-cobalt-sodium composite oxide, lithium-nickel-cobalt-barium composite oxide, lithium-nickel-cobalt-magnesium composite oxide, lithium-nickel-manganese-aluminum composite oxide, lithium-nickel-manganese-sodium composite oxide, lithium-nickel-manganese-barium composite oxide, lithium-nickel-manganese-magnesium composite oxide, lithium-nickel-aluminum-sodium composite oxide, lithium-nickel-aluminum-barium composite oxide, lithium-nickel - aluminum-magnesium composite oxide, lithium-nickel-sodium-barium composite oxide, lithium-nickel-sodium-magnesium composite oxide, lithium-nickel-barium-magnesium composite oxide, lithium-nickel-cobalt-manganese-aluminum Composite oxide, lithium-nickel-cobalt-manganese-sodium composite oxide, lithium-nickel-cobalt-manganese-barium composite oxide, lithium-nickel-cobalt-manganese-magnesium composite oxide, lithium-nickel-cobalt-aluminum - sodium composite oxide, lithium-nickel-cobalt-aluminum-barium composite oxide, lithium-nickel-cobalt-aluminum-magnesium composite oxide, lithium-nickel-cobalt-sodium-barium composite oxide, lithium-nickel-cobalt - sodium-magnesium composite oxide, lithium-nickel-cobalt-barium-sodium composite oxide, lithium-nickel-manganese-aluminum-sodium composite oxide , lithium-nickel-manganese-aluminum-barium composite oxide, lithium-nickel-manganese-aluminum-magnesium composite oxide, lithium-nickel-manganese-sodium-barium composite oxide, lithium-nickel-manganese-sodium-magnesium composite oxide, lithium-nickel-manganese-barium-magnesium composite oxide, lithium-nickel-aluminum-sodium-barium composite oxide, lithium-nickel-aluminum-sodium-magnesium composite oxide, lithium-nickel-sodium-barium- magnesium composite oxide, lithium-nickel-cobalt-manganese-aluminum-sodium composite oxide, lithium-nickel-cobalt-manganese-aluminum-barium composite oxide, lithium-nickel-cobalt-manganese-aluminum-magnesium composite oxide, Lithium-nickel-cobalt-manganese-sodium-barium composite oxide, lithium-nickel-cobalt-manganese-sodium-magnesium composite oxide, lithium-nickel-cobalt-manganese-barium-magnesium composite oxide, lithium-nickel-cobalt -aluminum-sodium-barium composite oxide, lithium-nickel-cobalt-aluminum-sodium-magnesium composite oxide, lithium-nickel-cobalt-sodium-nalium-magnesium composite oxide, lithium-nickel-manganese-aluminum-sodium- barium composite oxide, lithium-nickel-manganese-aluminum-sodium-magnesium composite oxide, lithium-nickel-manganese-sodium-barium-magnesium composite oxide, lithium-nickel-aluminum-sodium-barium-magnesium composite oxide, Lithium-nickel-cobalt-manganese-aluminum-sodium-barium composite oxide, lithium-nickel-cobalt-manganese-aluminum-sodium-magnesium composite oxide, lithium-nickel-manganese-aluminum-sodium-barium-magnesium composite oxide , lithium-nickel-cobalt-manganese-aluminum-sodium-barium-magnesium composite oxide). The composition ratio a of LiNi _a M _1-a O ₂ can be appropriately determined according to the energy density of the battery 10, for example. The energy density of the battery 10 increases as the composition ratio a increases. The composition ratio a is, for example, a≧0.50, preferably a≧0.80. In another example, the active material contained in the active material layer 120 (the active material layer 122 and the active material layer 124) is a composite oxide of lithium and a transition metal such as a lithium-cobalt composite oxide and a lithium-manganese composite oxide. transition metal sulfides such as _TiS2 , FeS and _MoS2 ; transition metal _oxides such as _MnO , _V2O5 , _V6O13 and _TiO2 ; The olivine-type lithium phosphate is, for example, at least one element selected from the group consisting of Mn, Cr, Co, Cu, Ni, V, Mo, Ti, Zn, Al, Ga, Mg, B, Nb and Fe. , lithium, phosphorus, and oxygen. These compounds may have some elements partially substituted with other elements in order to improve their properties. These substances may be used alone or in combination.

The density of the active material contained in the active material layer 120 (active material layer 122 and active material layer 124) is, for example, 2.0 g/cm ³ or more and 4.0 g/cm ³ or less, preferably 2.4 g/cm ³ or more. 3.8 g/cm ³ or less, more preferably 2.8 g/cm ³ or more and 3.6 g/cm ³ or less.

The thickness of the active material layer (active material layer 122 or active material layer 124) on one of both surfaces (first surface 112 and second surface 114) of current collector 110 may vary depending on the rate of battery 10, for example. can be determined as appropriate. The rate of the battery 10 increases as the thickness decreases. The thickness is, for example, 60 μm or less, preferably 50 μm or less, more preferably 40 μm or less.

The total thickness of the active material layers (active material layer 122 and active material layer 124) on both surfaces (first surface 112 and second surface 114) of current collector 110 is appropriately determined according to the rate of battery 10, for example. can do. The rate of the battery 10 increases as the thickness decreases. The thickness is, for example, 120 μm or less, preferably 100 μm or less, more preferably 80 μm or less.

Active material layer 120 (active material layer 122 and active material layer 124) can be manufactured, for example, as follows. First, slurry is prepared by dispersing an active material, a binder resin, and a conductive aid in an organic solvent. An organic solvent is, for example, N-methyl-2-pyrrolidone (NMP). Next, this slurry is applied onto the first surface 112 of the current collector 110 , the slurry is dried and, if necessary, pressed to form the active material layer 120 (active material layer 122 ) on the current collector 110 . to form The active material layer 124 can also be formed in the same manner.

The binder resin contained in the active material layer 120 (active material layer 122 and active material layer 124) is, for example, polytetrafluoroethylene (PTFE) or polyvinylidene fluoride (PVDF).

The amount of binder resin contained in active material layer 120 (active material layer 122 or active material layer 124) can be determined as appropriate. The active material layer 122 contains, for example, 0.1 parts by mass or more and 10.0 parts by mass or less, preferably 0.5 parts by mass or more and 5.0 parts by mass or less, with respect to 100 parts by mass of the total mass of the active material layer 122. More preferably, it contains 2.0 parts by mass or more and 4.0 parts by mass or less of binder resin. The same applies to the active material layer 124 as well.

The conductive aid contained in the active material layer 120 (active material layer 122 and active material layer 124) is, for example, carbon black, ketjen black, acetylene black, natural graphite, artificial graphite, carbon fiber, or the like. The graphite may be, for example, flake graphite or spherical graphite. These substances may be used alone or in combination.

The amount of the conductive aid contained in the active material layer 120 (the active material layer 122 or the active material layer 124) can be appropriately determined according to the cycle characteristics of the battery 10, for example. The cycle characteristics of the battery 10 are improved as the amount of the conductive agent in the active material layer 120 is increased. The active material layer 122 contains, for example, 3.0 parts by mass or more and 8.0 parts by mass or less, preferably 5.0 parts by mass or more and 6.0 parts by mass or less with respect to the total mass of 100 parts by mass of the active material layer 120. Contains a conductive aid. The same applies to the active material layer 124 as well.

The negative electrode 200 includes a current collector 210 and an active material layer 220 (an active material layer 222 and an active material layer 224). Current collector 210 has a first surface 212 and a second surface 214 . The second side 214 is opposite the first side 212 . The active material layer 222 is on the first surface 212 of the current collector 210 . An active material layer 224 is on the second surface 214 of the current collector 210 .

Current collector 210 may be formed of, for example, copper, stainless steel, nickel, titanium, or alloys thereof. The shape of the current collector 210 may be, for example, foil, flat plate, or mesh.

The active material layer 220 (active material layer 222 and active material layer 224) contains an active material and a binder resin. The active material layer 220 may further contain a conductive aid as needed.

The active material contained in the active material layer 220 (the active material layer 222 and the active material layer 224) is, for example, a carbon material such as graphite that occludes lithium, amorphous carbon, diamond-like carbon, fullerene, carbon nanotube, and carbon nanohorn. Lithium-based metal materials such as lithium metal and lithium alloy; Si-based materials such as Si, SiO ₂ , SiO _x (0<x≦2), Si-containing composite materials; Conductive polymer materials such as polyacene, polyacetylene, polypyrrole, etc. is. These substances may be used alone or in combination. In one example, active material layer 220 (active material layer 222 and active material layer 224) includes a first group of graphite particles (eg, natural graphite) having a first average particle size and a second group having a second average particle size. of graphite particles (eg, natural graphite). The second average particle size may be smaller than the first average particle size, the total mass of the graphite particles in the second group may be smaller than the total mass of the graphite particles in the first group, and the total mass of the graphite particles in the second group may be smaller than the first average particle size. The total mass may be, for example, 20 parts by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the total mass of the graphite particles in the first group.

The density of the active material contained in the active material layer 220 (active material layer 222 and active material layer 224) is, for example, 1.2 g/cm ³ or more and 2.0 g/cm ³ or less, preferably 1.3 g/cm ³ or more. It is 1.9 g/cm ³ or less, more preferably 1.4 g/cm ³ or more and 1.8 g/cm ³ or less.

The thickness of the active material layer (active material layer 222 or active material layer 224) on one of both surfaces (first surface 212 and second surface 214) of current collector 210 may vary depending on the rate of battery 10, for example. can be determined as appropriate. The rate of the battery 10 increases as the thickness decreases. The thickness is, for example, 60 μm or less, preferably 55 μm or less, more preferably 50 μm or less.

The total thickness of the active material layers (active material layer 222 and active material layer 224) on both surfaces (first surface 212 and second surface 214) of current collector 210 is appropriately determined according to, for example, the rate of battery 10. can do. The rate of the battery 10 increases as the thickness decreases. The thickness is, for example, 120 μm or less, preferably 110 μm or less, more preferably 100 μm or less.

The active material layer 220 (active material layer 222 and active material layer 224) can be manufactured, for example, as follows. First, an active material and a binder resin are dispersed in a solvent to prepare slurry. The solvent may be, for example, an organic solvent such as N-methyl-2-pyrrolidone (NMP), or may be water. Next, this slurry is applied onto the first surface 212 of the current collector 210 , the slurry is dried, and if necessary, pressing is performed to form the active material layer 220 (active material layer 222 ) on the current collector 210 . to form The active material layer 224 can also be formed in a similar manner.

The binder resin contained in the active material layer 220 (the active material layer 222 and the active material layer 224) is, for example, a binder resin such as polyvinylidene fluoride (PVDF) when an organic solvent is used as the solvent for obtaining the slurry. When water is used as the solvent for obtaining the slurry, it can be, for example, a rubber-based binder (eg, SBR (styrene-butadiene rubber)) or an acrylic binder resin. Such a water-based binder resin may be in the form of an emulsion. When water is used as the solvent, it is preferable to use an aqueous binder and a thickener such as CMC (carboxymethyl cellulose) in combination.

The amount of binder resin contained in active material layer 220 (active material layer 222 or active material layer 224) can be determined as appropriate. The active material layer 222 is, for example, 0.1 parts by mass or more and 10.0 parts by mass or less, preferably 0.5 parts by mass or more and 8.0 parts by mass or less with respect to 100 parts by mass of the total mass of the active material layer 222. More preferably from 1.0 parts by mass to 5.0 parts by mass, still more preferably from 1.0 parts by mass to 3.0 parts by mass of a binder resin. The same applies to the active material layer 224 as well.

Separator 300 includes base material 310 and insulating layer 320 (insulating layer 322 and insulating layer 324). Substrate 310 has a first side 312 and a second side 314 . The second side 314 is opposite the first side 312 . An insulating layer 322 is on the first side 312 of the substrate 310 . An insulating layer 324 is on the second side 314 of the substrate 310 .

In the example shown in FIG. 3, separator 300 includes insulating layers 320 (insulating layer 322 and insulating layer 324) on both sides (first side 312 and second side 314) of substrate 310. In the example shown in FIG. In another example, separator 300 may include insulating layer 320 on only one of the two surfaces (first surface 312 and second surface 314) of substrate 310. FIG.

The separator 300 has a function of electrically insulating the positive electrode 100 and the negative electrode 200 and allowing ions (for example, lithium ions) to pass therethrough. Separator 300 can be, for example, a porous separator.

The shape of the separator 300 can be appropriately determined according to the shape of the positive electrode 100 or the negative electrode 200, and can be rectangular, for example.

Base material 310 preferably includes a resin layer containing a heat-resistant resin. The resin layer contains a heat-resistant resin as a main component, and specifically, 50 parts by mass or more, preferably 70 parts by mass or more, more preferably 90 parts by mass with respect to 100 parts by mass of the total mass of the resin layer. The above heat-resistant resin is included, and 100 parts by mass of the heat-resistant resin may be included with respect to 100 parts by mass of the total mass of the resin layer. The resin layer may be a single layer or two or more layers.

Heat-resistant resins include, for example, polyethylene, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, poly-m-phenylene terephthalate, poly-p-phenylene isophthalate, polycarbonate, polyester carbonate, aliphatic polyamide, wholly aromatic polyamide, semi- Aromatic polyamide, wholly aromatic polyester, polyphenylene sulfide, polyparaphenylenebenzobisoxazole, polyimide, polyarylate, polyetherimide, polyamideimide, polyacetal, polyetheretherketone, polysulfone, polyethersulfone, fluorine resin, poly It is one or two or more selected from ether nitriles, modified polyphenylene ethers, and the like.

The insulating layer 320 (insulating layer 322 and insulating layer 324) can be manufactured, for example, as follows. First, an inorganic filler and a resin are dispersed in a solvent to prepare a solution. Examples of solvents include water, alcohols such as ethanol, N-methylpyrrolidone (NMP), toluene, dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and the like. Next, a solution is applied on the first surface 312 of the base material 310 to form the insulating layer 320 (insulating layer 322). The insulating layer 324 can also be formed in a similar manner.

Materials forming the inorganic filler contained in the insulating layer 320 (insulating layers 322 and 324) include, for example, magnesium hydroxide, aluminum oxide, boehmite, titanium oxide, silicon oxide, magnesium oxide, barium oxide, zirconium oxide, oxide It is one or more selected from zinc, iron oxide and the like. For example, from the viewpoint of improving the resistance of the nail penetration test, the material is preferably magnesium hydroxide.

The resin contained in the insulating layer 320 (insulating layer 322 and insulating layer 324) includes, for example, aramid (aromatic polyamide) resin such as meta-aramid and para-aramid; cellulose resin such as carboxymethyl cellulose (CMC); acrylic system resin; fluororesin such as polyvinylidene fluoride (PVDF); Among these, aramid (aromatic polyamide)-based resins are preferred, and meta-aramid is more preferred. These substances may be used alone or in combination.

The thickness of the base material 310 can be determined as appropriate, and can be, for example, 5.0 μm or more and 10.0 μm or less, preferably 6.0 μm or more and 10.0 μm or less.

The total thickness of the insulating layer 322 and the insulating layer 324 can be determined as appropriate. can.

The thickness of the separator 300 can be determined as appropriate, and can be, for example, 15.0 μm or more and 30.0 μm or less, preferably 16.0 μm or more and 27.5 μm or less.

In the example shown in FIG. 3 , the positive electrode 100 , the negative electrode 200 and the separator 300 are such that the first surface 112 of the positive electrode 100 faces the second surface 314 of the separator 300 and the second surface 214 of the negative electrode 200 faces the first surface 314 of the separator 300 . They overlap each other so as to face the surface 312 .

(Example 1)
A battery 10 was manufactured as follows.

A positive electrode 100 was formed as follows. First, a slurry was prepared by dispersing the following materials in an organic solvent.
Active material: 94.0 parts by mass of lithium-nickel-containing composite oxide (chemical formula: _{Li ( Ni0.80Co0.15Al0.05} ) _O2 )
Conductive agent: 2.0 parts by mass of spherical graphite and 1.0 parts by mass of flake graphite Binder resin: 3.0 parts by mass of polyvinylidene fluoride (PVDF)
Next, this slurry is applied on both sides (first surface 112 and second surface 114) of a 15 μm aluminum foil (current collector 110), the slurry is dried, and pressed to form an active material layer 120 (active material layer 120). A material layer 122 and an active material layer 124) were formed. The density of the active material of the active material layer 122 is 3.35 g/cm ³ and the thickness of the active material layer 122 is 36.6 μm. The density of the active material of the active material layer 124 is 3.35 g/cm ³ and the thickness of the active material layer 124 is 36.6 μm.

A negative electrode 200 was formed as follows. First, a slurry was prepared by dispersing the following materials in water.
Active material: 77.36 parts by mass of natural graphite (average particle size: 16.0 µm) and 19.34 parts by mass of natural graphite (average particle size: 10.5 µm)
Conductive agent: 0.3 parts by mass of spherical graphite Binder resin: 2.0 parts by mass of styrene-butadiene rubber (SBR)
Thickener: 1.0 part by weight of carboxymethylcellulose (CMC)
Next, this slurry is applied on both sides (first surface 212 and second surface 214) of an 8 μm copper foil (current collector 210), the slurry is dried, and pressed to form an active material layer 220 (active material layer 220). A material layer 222 and an active material layer 224) were formed. The active material density of the active material layer 222 is 1.55 g/cm ³ and the thickness of the active material layer 222 is 50.0 μm. The density of the active material of the active material layer 224 is 1.55 g/cm ³ and the thickness of the active material layer 224 is 50.0 μm.

Separator 300 was formed as follows. First, the following materials were dispersed in a solvent to prepare a solution.
Inorganic filler: magnesium hydroxide Resin: meta-aramid Next, this solution is applied on both sides (first surface 312 and second surface 314) of a 6.0 μm polyethylene film (base material 310) to form an insulating layer 320 (insulating layer 320). A layer 322 and an insulating layer 324) were formed. The total thickness of the insulating layer 322 (8.0 μm) and the thickness of the insulating layer 324 (8.0 μm) is 16.0 μm.

The laminate 12 was formed such that 14 positive electrodes 100 and 14 negative electrodes 200 were alternately arranged and the separators 300 were folded in a zigzag manner, as shown in FIG.

The battery 10 was manufactured by housing the laminate 12 together with the electrolytic solution in the exterior material 400 as shown in FIG. The electrolyte contains _LiPF6 .

A nail penetration test was performed on the battery 10 . Specifically, when the SOC (State Of Charge) of the battery 10 was fully charged, a nail (SUS304) with a diameter of 3 mm was stuck into the center of the battery 10 at 80 mm/s at room temperature. Nail penetration test resistance of battery 10 was evaluated according to the following criteria.
◎: No ignition was observed 3 minutes after the start of the test ○: No ignition was observed within 3 minutes after the start of the test (ignition was observed 3 minutes after the start of the test)
×: Ignition was observed within 10 seconds from the start of the test

(Example 2)
In Example 2, the thickness of the base material 310 is 9.0 μm, and the total thickness of the insulating layer 322 (8.0 μm) and the insulating layer 324 (8.0 μm) is 16.0 μm. It was the same as Example 1 except for the points.

(Comparative example 1)
In Comparative Example 1, the thickness of the base material 310 is 7.5 μm, and the total thickness of the insulating layer 322 (3.75 μm) and the insulating layer 324 (3.75 μm) is 7.5 μm. It was the same as Example 1 except for the points.

(Comparative example 2)
In Comparative Example 2, the thickness of the base material 310 is 9.0 μm, and the total thickness of the insulating layer 322 (6.0 μm) and the insulating layer 324 (6.0 μm) is 12.0 μm. It was the same as Example 1 except for the points.

Table 1 shows the respective results of Example 1, Example 2, Comparative Example 1 and Comparative Example 2.

The results shown in Table 1 suggest that the nail penetration test resistance can be improved according to the ratio of the thickness of the insulating layer 320 to the thickness of the substrate 310 . Specifically, it can be said that the higher the ratio of the thickness of the insulating layer 320 to the thickness of the base material 310 is, the more the nail penetration test resistance is improved. From the result of Example 2 (the ratio of the thickness of the insulating layer 320 to the thickness of the base material 310: about 1.78), the ratio of the thickness of the insulating layer 320 to the thickness of the base material 310 is 1.50 or more. It can be said that From the result of Example 1 (the ratio of the thickness of the insulating layer 320 to the thickness of the base material 310: about 2.67), the ratio of the thickness of the insulating layer 320 to the thickness of the base material 310 is 3.00 or less. It can be said that

The reason why the nail penetration test resistance can be improved according to the ratio of the thickness of the insulating layer 320 to the thickness of the base material 310 is presumed as follows. In the nail penetration test, the positive electrode 100 and the negative electrode 200 are short-circuited through the nail, and heat can be generated from the nail. Around the area where the nail stays through, the substrate 310 may shrink away from the nail due to the heat generated by the nail, while the insulating layer 320 inhibits the shrinkage of the substrate 310 . obtain. If the base material 310 (that is, the entire separator 300) contracts because the insulating layer 320 cannot sufficiently suppress the contraction of the base material 310, the positive electrode 100 and the negative electrode 200 come into direct contact with each other around the nail and catch fire. can. On the other hand, as described above, when the ratio of the thickness of the insulating layer 320 to the thickness of the base material 310 is large (that is, when the thickness of the base material 310 is small and the thickness of the insulating layer 320 is large) , the shrinkage of the base material 310 can be suppressed by the insulating layer 320, and the nail penetration test resistance can be improved.

Although the embodiments and examples of the present invention have been described above with reference to the drawings, these are examples of the present invention, and various configurations other than those described above can be adopted.
Examples of reference forms are added below.
1. an electrode capable of functioning as a positive electrode or a negative electrode;
a separator including a base material and an insulating layer;
including
The electrode comprises a current collector having a first surface and a second surface opposite to the first surface, and an active material layer positioned on the first surface of the current collector and having a thickness of 60 μm or less. and including
A battery, wherein the ratio of the thickness of the insulating layer to the thickness of the base material is 1.50 or more and 3.00 or less.
2. 1. In the battery described in
The battery, wherein the insulating layer contains magnesium hydroxide.
3. 1. or 2. In the battery described in
The battery, wherein the insulating layer further includes an aromatic polyamide.
4. 1. to 3. In the battery according to any one of
The positive electrode includes an active material layer,
The battery, wherein the active material layer of the positive electrode contains 5.0 parts by mass or more of a conductive aid with respect to 100 parts by mass of the total mass of the active material layer of the positive electrode.
5. 1. to 4. In the battery according to any one of
The battery, wherein the separator is folded back in a serpentine manner such that a portion of the separator is positioned between the adjacent positive and negative electrodes.

10 Battery 12 Laminated body 100 Positive electrode 110 Current collector 112 First surface 114 Second surface 120 Active material layer 122 Active material layer 124 Active material layer 130 First lead 200 Negative electrode 210 Current collector 212 First surface 214 Second surface 220 Active material layer 222 Active material layer 224 Active material layer 230 Second lead 300 Separator 310 Base material 312 First surface 314 Second surface 320 Insulating layer 322 Insulating layer 324 Insulating layer 400 Exterior material

Claims (5)

an electrode capable of functioning as a positive electrode or a negative electrode;
a separator comprising a substrate, a first insulating layer located on one of both surfaces of the substrate, and a second insulating layer located on the other of both surfaces of the substrate ;
including
The electrode comprises a current collector having a first surface and a second surface opposite to the first surface, and an active material layer positioned on the first surface of the current collector and having a thickness of 60 μm or less. and including
The first insulating layer and the second insulating layer contain an inorganic filler and a resin,
A battery, wherein a ratio of the sum of the thickness of the first insulating layer and the thickness of the second insulating layer to the thickness of the base is 1.50 or more and 3.00 or less. The battery of claim 1,
A battery , wherein at least one of the materials forming the inorganic filler is magnesium hydroxide. In the battery according to claim 1 or 2,
A battery , wherein at least one of the resins is an aromatic polyamide. In the battery according to any one of claims 1 to 3,
The positive electrode includes an active material layer,
The battery, wherein the active material layer of the positive electrode contains 5.0 parts by mass or more of a conductive aid with respect to 100 parts by mass of the total mass of the active material layer of the positive electrode. In the battery according to any one of claims 1 to 4,
The battery, wherein the separator is folded back in a serpentine manner such that a portion of the separator is positioned between the adjacent positive and negative electrodes.

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